diff --git a/developer/services/qrexec-internals.md b/developer/services/qrexec-internals.md index 864a38a5..0a4b5d64 100644 --- a/developer/services/qrexec-internals.md +++ b/developer/services/qrexec-internals.md @@ -15,15 +15,23 @@ redirect_from: A [general introduction](/doc/qrexec/) to qrexec is also available. For the implementation of qrexec2, see [here](/doc/qrexec2/#qubes-rpc-internals).*) -The qrexec framework consists of a number of processes communicating with each other using common IPC protocol (described in detail below). +The qrexec framework consists of a number of processes communicating with each other using a common IPC protocol, described in detail below. + Components residing in the same domain (`qrexec-client-vm` to `qrexec-agent`, `qrexec-client` to `qrexec-daemon`) use local sockets as the underlying transport medium. Components in separate domains (`qrexec-daemon` to `qrexec-agent`, data channel between `qrexec-agent`s) use vchan links. Because of [vchan limitation](https://github.com/qubesos/qubes-issues/issues/951), it is not possible to establish qrexec connection back to the source domain. ## Dom0 tools implementation +The following programs handle parts of the framework: sending and receiving requests, verifying permissions, and administering connections. +These tools are not designed to be used by users directly. + ### qrexec-daemon -* `/usr/sbin/qrexec-daemon`: One instance is required for every active domain. Responsible for: + +`/usr/sbin/qrexec-daemon` + +One instance is required for every active domain. +Responsible for: * Handling execution and service requests from **dom0** (source: `qrexec-client`). * Handling service requests from the associated domain (source: `qrexec-client-vm`, then `qrexec-agent`). * Command line: `qrexec-daemon domain-id domain-name [default user]` @@ -32,26 +40,41 @@ Because of [vchan limitation](https://github.com/qubesos/qubes-issues/issues/951 * `default user`: Optional. If passed, `qrexec-daemon` uses this user as default for all execution requests that don't specify one. ### qrexec-policy -* `/usr/bin/qrexec-policy`: Internal program used to evaluate the RPC policy and deciding whether a RPC call should be allowed. + +`/usr/bin/qrexec-policy` + +Internal program used to evaluate the RPC policy and decide whether an RPC call should be allowed. ### qrexec-client -* `/usr/bin/qrexec-client`: Used to pass execution and service requests to `qrexec-daemon`. Command line parameters: + +`/usr/bin/qrexec-client` + +Used to pass execution and service requests to `qrexec-daemon`. +Command line parameters: * `-d target-domain-name`: Specifies the target for the execution/service request. * `-l local-program`: Optional. If present, `local-program` is executed and its stdout/stdin are used when sending/receiving data to/from the remote peer. * `-e`: Optional. If present, stdout/stdin are not connected to the remote peer. Only process creation status code is received. * `-c `: used for connecting a VM-VM service request by `qrexec-policy`. Details described below in the service example. * `cmdline`: Command line to pass to `qrexec-daemon` as the execution/service request. Service request format is described below in the service example. -**Note:** None of the above tools are designed to be used by users directly. - ## VM tools implementation -### `qrexec-agent`: One instance runs in each active domain. Responsible for: +### `qrexec-agent` + + + +One instance runs in each active domain. +Responsible for: * Handling service requests from `qrexec-client-vm` and passing them to connected `qrexec-daemon` in dom0. * Executing associated `qrexec-daemon` execution/service requests. * Command line parameters: none. -### `qrexec-client-vm`: Runs in an active domain. Used to pass service requests to `qrexec-agent`. +### `qrexec-client-vm` + + + +Runs in an active domain. +Used to pass service requests to `qrexec-agent`. * Command line: `qrexec-client-vm target-domain-name service-name local-program [local program arguments]` * `target-domain-name`: Target domain for the service request. Source is the current domain. * `service-name`: Requested service name. @@ -82,7 +105,7 @@ Details of all possible use cases and the messages involved are described below. ### dom0: request execution of `some_command` in domX and pass stdin/stdout -![qrexec basics diagram](/attachment/wiki/qrexec3/qrexec-internals-dom0.png) +![qrexec internals diagram dom0](/attachment/wiki/qrexec3/qrexec-internals-dom0.png) - **dom0**: `qrexec-client` is invoked in **dom0** as follows: @@ -119,7 +142,7 @@ Details of all possible use cases and the messages involved are described below. ### domY: invoke execution of qubes service `qubes.SomeRpc` in domX and pass stdin/stdout -![qrexec basics diagram](/attachment/wiki/qrexec3/qrexec-internals-domY.png) +![qrexec internals diagram domY](/attachment/wiki/qrexec3/qrexec-internals-domY.png) - **domY**: `qrexec-client-vm` is invoked as follows: